DE4120016C1 - - Google Patents

Abstract

An extruder for difficult-to-mix extrudates is presented, in which the pin-lined barrel and transfer mixing sections, known per se and until now only used individually, are used together in one extruder. Restricting pins, arranged in the transfer mixing section in the region of the greatest barrel channel volume, permit universal use of the extruder with respect to the extrudate. The combination of both mixing systems surprisingly allows an increase in the material throughput of 60% to 100% while maintaining the same mixing quality and halving the drive torque. Due to a constant number of barrel and screw channels, the number of barrel and screw flights remains independent of the channel cross-sectional area of barrel and screw. A spiral barrel groove in the feed zone of the extruder barrel additionally improves the mixing quality of the extrudate and the output of the extruder. <IMAGE>

Description

The invention relates to an extruder for processing and manufacturing of rubber and thermoplastic materials according to the generic term of claim 1 and according to the main patent 40 39 942.

As a discharge and homogenization extruder are in the past consistently used the so-called barrel extruders, as for example by DE-OS 22 35 784 or DE-OS 30 03 615 the applicant is known. For extruders of this type metal pins protrude radially through the extruder housing into the processing room of the extruder, the extruder screw in this Zone has interrupted screw flights.

These extruders are characterized by a very high output and good homogenization on the material to be processed and also allow an enlarged at high screw speed Material throughput per unit of time compared to conv  tional cold feed extruders with shear part screw. These benefits have led to pin cylinder extruders in the last 15 Years of the most commonly used extruders in rubber Industry.

Regardless of this, an extruder mixing part was developed, which as Transfer mixing part has become known (DE-A 11 42 839). This Mixing part is essentially characterized in that both the Extruder screw as well as the inner wall of the extruder barrel over a certain length is provided with grooves and webs, whereby in Longitudinal direction of the extruder housing is the depth of the extruder screw decreases to the same extent to zero and then grows again, how the pitch of the housing grooves increases or decreases again. This design of extruder screw and housing a complete exchange of extrudate between the screw grooves and the housing grooves possible, which causes a good mixing effect.

The transfer extruder could be compared to the pin cylinder extruder claim a certain market share, especially if the overall length of the extruder should be kept small.

In addition, from US 36 13 160 extruder with throttle components is known to be provided with which the extrudate transport in the extruder is variable from can be controlled externally. According to this document is on the screw shaft of the extruder screw is approximately cylindrical Component arranged that rotates with the screw and the processing room completely blocked downstream. In the area of this cylindrical Due to the extruder housing, two throttle pins are part of the component radially in an axially aligned overflow channel performed, which worked into the inner wall of the extruder barrel is.  

With throttle pins withdrawn, part of the upstream of the cylindrical component located extrudate through these channels get to the downstream extruder part. Through different depths Driving the throttle pins into these overflow channels, leaves limit this extrudate flow.

In addition, a transfer extruder is known from DE-PS 27 31 438 which the number of webs in the housing and on the screw in Transfer area with increasing cross-sectional area of the screw flights reduced, and with decreasing cross-sectional area of the Auger speeds increased. They have worm threads with a larger cross-sectional area a larger width than worm gear with a smaller one Cross sectional area.

The tests carried out on such mixed parts in the past have shown that they have comparatively good mixed qualities can be achieved, and that the mixing part is completely self-cleaning is. The disadvantage, however, was that the construction proposed there caused a relatively high production cost, which is why the manufacturing costs were high.

Finally, it is known from DE-OS 31 33 708 and EP-PS 00 62 203, in the case of single-screw extruders, the inside of the extruder housing in the feed area with axial or helical housing grooves Mistake. Such extruders are usually used for the extrusion of Polymer materials with high melt viscosity, low thermal Stability or low surface friction against the metal surfaces of the extruder processing room. Such an extruder allows even with such difficult to process extrudates high output at low melting temperatures and high Mass pressures. In addition, reduced shear in the Feed zone of the extruder plasticizes the extrudate gently and  be extruded without pulsation.

Since the technology of the mixing extruders, apart from improvements in details, has not changed in the past 15 years, the Invention, the object of a mixing and homogenizing extruder to introduce the compared to the known devices with reduced investment costs at least the same good mixing effect allows an increased output, a significantly shorter overall length and an expansion of the previous one Areas of application of mixing and homogenizing extruders allowed.

Finally, the plasticizing work that can be achieved with this extruder should be depending on the properties of the extrudate be freely adjustable.

This problem was solved with an extruder construction, as it results from the features of the main claim. Beneficial Refinements and developments of the invention are the See subclaims.

By combining the two known mixed part designs an extruder with the features of the main claim are created, compared to the mixing and homogenizing extruders according to the prior art technology has significant advantages.

So with one over a pin cylinder area and one transfer area with extruders equipped with additional pins be that with the same mixing quality and the same screw speed the drive power of the extruder is reduced by up to 50% and the Mass throughput could be increased up to 60% to 100%.

These excellent results also cause a 50% reduction  adornment of the drive torque, which in the manufacture of the extruder leads to a sharp reduction in transmission costs. In addition can be achieved by connecting the pin cylinder and the transfer part technology the component length required for the same mixing quality of the mixing area by approx. 50% compared to an extruder reduce, which only works according to the pin cylinder principle.

Due to the arrangement of radially adjustable throttle pins, which in protrude the part of the transfer area of the extruder barrel radially, in which the case aisles have approximately their largest aisle volume, the proposed extruder for processing different rubber compounds. With the depth of penetration the throttle pins in the housing aisles and the processing space of the extruder, the plasticizing performance or the friction energy converted in the transfer part for the extrudate Preselect as required and mix-related. This can be compared to the previously known generic extruders in addition to the screw speed and the process part temperature to another freely selectable process parameters.

The design of the extruder screw and the housing bush in the transfer area with regard to the independence of the number of gears and thus the number of bridges from the aisle cross-sectional area also allows an inexpensive Manufacturing while maintaining self-cleaning ability and mixing quality of the extruder.

Finally, the use of housing grooves known per se permits in the feed area of the extruder in combination with the pin cylinder and transfer part another surprising improvement of Mixing quality and output of the extruder.

Especially for rubber-based extrudates that are difficult to process  an extruder feed area proved to be particularly advantageous, with a helical groove in the inner wall of the extruder housing was incorporated below the filler opening of the extruder had its starting point and downstream along a length of about 3 screw diameters was formed.

The groove had a maximum depth of about 1 cm and a constant Width of 2.5 cm and ran slowly at the ends of the Ge inside diameter. The slope of the groove corresponded approximately that of the extruder screws in the feed area.

The output could be reduced with a feed area designed in this way of the extruder and significantly improve the mixing quality of the extrudate increase even further. Test series with an extruder with less Groove depth (approx. 0.5 cm) showed significant deterioration both in terms of working behavior and in terms of mixing quality. Furthermore could be verified that the same extruder with the described Grooves in the feed area and the described transfer part, but without the pin cylinder part arranged in front of this transfer part, produced a significantly poorer mix quality. Special and extrudates such as rubber that are difficult to mix continuously Mixtures for curb chain tunnels, could be with such Mix extruder unsatisfactorily. This makes it clear that the combination of pin cylinder part and transfer part for the desired Mixing result with such extrudates is necessary. The helical groove improves the mixing quality and the output of the Extruders only go further.

The invention can be described using exemplary embodiments and Explain with the help of the drawing.

It shows in  

Fig. 1 shows a longitudinal section through a single-screw extruder without throttle pins in the transfer section,

Fig. 2 is a longitudinal section through a single screw extruder with throttle pins in the transfer section,

Fig. 3a-c the graphical representation of test results with an extruder of the proposed design in comparison to conventional pin extruder,

Fig. 4 is a schematic side view of a transfer screw portion,

Fig. 5 is a schematic side view of a cut transfer bushing part,

Fig. 6 is a developed view of the socket part according to Fig. 5,

Fig. 7 is a longitudinal section through the extruder barrel in the area of the feed zone.

Fig. 1 shows a schematic longitudinal section through a screw extruder 1. Inside the extruder housing 2 , an extruder screw 6 is arranged, which can be driven by a drive unit 5 about its longitudinal axis. The extruder housing 2 has in the region of its upstream end an inlet opening 3 for the material to be extruded, which leaves the extruder ready mixed and homogenized through the outlet opening 4 .

The extruder screw 6 has a screw geometry in the feed region 9 which is suitable for drawing the material fed through the inlet opening 3 into the extruder and plasticizing it in a manner known per se.

A pin cylinder area 7 is provided downstream of this feed area, in which two rows of pins 11 protrude radially through the extruder housing 2 in the direction of the screw axis into the processing space 14 of the extruder. In this pin barrel section 7, the screw flights are interrupted 12 in a known manner into the pin plane to colliding with the pins 11 to be avoided.

A transfer area 8 is arranged downstream of the pin cylinder area 7 , in which in this exemplary embodiment the angles between the screw webs 18 of the extruder screw 6 and the housing webs 13 of the extruder housing 2 are greater than or equal to 105 ° and do not form any complementary angles with one another to 90 °.

The transfer area 8 can be divided into an inlet area and an outlet area, the two areas being separated from one another by the housing aisle with the greatest aisle depth.

In this transfer area 8 of the extruder, the number of gears in the inlet and outlet areas is constant, so that the number of webs in the inlet and outlet areas is independent of the gear cross-section of the housing or worm gears 16 , 15 .

The last part of the process of the extruder screw 6 is formed by the pressure increasing area 10 , in which the screw geometry is selected so that the melt pressure can be raised to the necessary tool pressure in a known manner.

In addition to this exemplary embodiment, other implementation options for this pin transfer extruder are also conceivable. For example, the transfer area 8 could also be arranged upstream from the pin cylinder area 7 , although the variant presented above produces the better mixing and homogenization results. It should also be noted here that the pin cylinder area also fulfills its mixing and homogenizing task with more than two rows of pins. In terms of the cost-mix quality ratio, the pin cylinder area is best equipped with one to five rows of pins.

The preferred length of the individual extruder areas is one Extruder length of 10 screw diameters (D) about 3 D for the feed area, 1.5 to 10 D, preferably 1.5 to 2 D for the pen cylinder range, 2 to 2.5 D for the transfer range and approx. 3 D for the pressure build-up area.

Irrespective of this information, however, can also be used as required additional process areas before, after or between the pin cylinder and transfer areas can be arranged, e.g. B. degassing or kneading areas.

In FIG. 2, a pin transfer extruder 1 is shown with throttle pins 11 in the transfer member. The filling area 9 of this extruder also corresponds to the usual cold feed extruder and has a ratio of screw length (D) to screw diameter of three.

Downstream of the filling area 9 is an extruder section with a total length of 6 D, in which the pin cylinder area 7 with two pin planes with pins 11 arranged one behind the other is located. Downstream of the pin cylinder area 7 , the transfer area 8 is provided with approximately 2 D and the pressure build-up area 9 with approximately 1.5 D length.

The temperature of the extruder barrel 2 is carried out in a known manner by means of temperature control channels 19 in the housing wall 2 . The transfer part of the extruder housing is locked in this embodiment as a housing bushing 20 in the extruder housing 2 .

The pitch of the threads of the extruder screw and housing bush in the transfer part are chosen so that the webs between the screw and the socket form an angle equal to or more than 105 °. This results in an advantageous manner that the extrudate when passing this Transfer part, due to the resulting large number of intersections between worm and bush webs per Screw rotation, is subjected to an intensive shearing process.

In contrast to the worm threads, the socket threads are in the transfer part not interrupted. Rather, they twist continuously and continuously from the entry zone of the transfer part to its exit zone roughly increasing or decreasing spiral or helical around the imaginary Longitudinal axis of the extruder.

In the first third of the transfer part, the screw core diameter increases from the max. Aisle depth down to the outside diameter, ie the aisle volume of the extruder screw 6 drops from the maximum value in the inlet area to zero. The passage volumes of the housing bushing 20 have the opposite tendency. The passage volume effectively present for the extrudate is thus kept constant in the axial and radial transport directions. Due to these circumstances, there is inevitably a 100 percent extrudate exchange between extruder screw 6 and housing bushing 20 .

When approximately 1.4 D long exit region of the transfer portion in FIG. 2 takes the intermediate volume of the extruder screw 6 from continuous continuous and to the female housing 20, again using the existing for the extrudate total transition volume of screw and jack is kept constant.

In this exemplary embodiment too, the number of flights in the inlet area and in the outlet area of the transfer area 8 is constant, as a result of which the number of screw and housing bush webs is independent of the screw and housing flight cross-sectional area.

Extensive investigations resulted in this, in particular in the processing of highly viscous natural rubber mixtures, that Preplasticization of the extruder in the pin area with low shear gradients before the intensive plasticizing work in the transfer part both increasing output and positive for pulsation behavior of the machine.

In addition to the screw speed and the process part temperatures the machine via another process parameter that can be freely selected and the universality of the machine in terms of processability a wide range of different rubber compounds expanded.

In this embodiment, at the end of the first third of the transfer area 8 there is a throttle element, which has throttle pins 17 distributed symmetrically on the circumference of the transfer component, which radially plunge into the uninterrupted gears of the housing bush 20 and the gear volume of the housing bush 20 in this range from maximum value to can reduce to zero.

With these throttle pins 17 , which are adjusted either manually or hydraulically from the outside, the plasticizing performance or the friction energy converted in the transfer part can be predetermined as desired for the extrudate.

These throttle pins 17 can be attributed, among other things, to the fact that for the first time the pin transfer extruder was able to process rubber compound grades that had previously not been able to be processed with sufficient homogeneity with cold feed extrusion, also through the use of specially optimized pin cylinder extruders. These are natural rubber grades, for example for the production of curb chain tunnels as well as tread compound with the same base polymer for truck and EM tires.

To summarize the results achieved so far with a GE 150 ST × 9D extruder Test results together, so you can see that in comparison to the barrel extruder for low-viscosity synthetic Rubber compounds up to viscosities from 55 to 60 ML 1 + 4 (100 ° C) to achieve output increases of 25% to 50% are, with a reduction of the specific energy up to 20%.

For highly viscous, difficult to process natural rubber grades the advantages are still between 90 to 120 ML 1 + 4 (100 ° C) more relevant because, as it turned out, the pin cylinder extruder Extrudate homogeneity limit already at approx. 800-1000 kg / h output is achieved and thus, in individual cases, doubled the performance of the Pen transfer extruders appear possible.

FIGS. 3 a-c show experimental results in a graphical representation which with an extruder according to the prior art (dashed Curves) and a laboratory transfer pen extruder (solid Curves) of comparable size. An extrudate was used Natural rubber compound NK 90-95 ML 1 + 4 (100 ° C) used as  is highly viscous and is particularly difficult to process. In All three representations are marked with a vertical line Hatching marks the speed of 25 revolutions per minute until to the conventional extruder with reasonable quality Rubber compound could process.

In FIG. 3a the rubber output is plotted as a function of the screw speed, while FIG. 3b shows the melt temperature and FIG. 3c the specific energy requirement per kg of extrudate as a function of the screw speed. The composition of these three graphics shows that with the extruder concept proposed here, with an excellent mixing and homogenizing effect, high extrudate output at an acceptable extrudate temperature and considerably reduced energy consumption is possible.

In addition, there were problems with product porosity in the profile, that with the barrel extruder already in the lower performance range occurred, could not be determined at all with the pen transfer extruder were.

In FIG. 4, in one embodiment, the extruder screw 6 is illustrated in the transfer region 8. The basically known increase or decrease in the screw flight cross-sectional area in the inlet or outlet area is brought about here only by the conical change in the core cross section, that is to say the flight depth, of the screw. The number of gears in the inlet and outlet area is different from one another, but constant in the respective area. The result of this is that the number of webs is independent of the aisle cross-sectional area 22 .

Fig. 4 is also removed in a further embodiment in that the transfer screw in the region of the maximum Extrudatübergabe to the housing passages so as, in the field has the throttle pins 17 via grooves 23 in the screw core. Although these grooves 23 connect the screw flights in the inlet and outlet area with one another, they do not allow material to be transported through them due to their small depth of approximately 1 mm and their small width of approximately 10 mm. Rather, the mixing performance of the transfer area can be improved even with difficult extrudates. This is done essentially by providing additional shaving edges through these grooves.

FIG. 5 shows a schematic longitudinal section through a housing bush 20 which interacts with the extruder screw in the transfer area according to FIG. 4. Here, too, it becomes clear that the number of housing gears is constant in the inlet and outlet areas, so that the number of housing webs remains independent of the cross-sectional area of the aisle.

By this construction, a reinvigorating mixing quality with very good self-cleaning action on the one hand ensured, while that of the production cost while at the same wide housing (and worm) transitions is particularly evident in connection with the handling of the female component according to Fig. 5 and Fig. 6 is significantly reduced becomes.

In addition, it should be pointed out that the proposed pin cylinder extruder can be used with or without a throttle pin in the transfer area, although throttle pins should not be dispensed with in the optimal design. Finally, the positioning of the extruders allows them to be adjusted to a wide variety of rubber compounds and their processing parameters and can therefore be used universally by the user. In an imperfect embodiment, the adjustable throttle pins can also be arranged at the downstream end of the extruder, for example at the end of the pressure build-up area 10 .

Finally, FIG. 7 shows a longitudinal section through the extruder housing 2 with a groove 24 in the feed zone 8 . In this exemplary embodiment, the helical groove 24 has a depth of approximately 1 cm and a width of approximately 2.5 cm, although other groove depths and widths are also conceivable. However, the groove depth should not be greater than the groove width and the groove depth and groove width should not be less than 0.3 cm. The slope of the groove 24 corresponds approximately to the slope of the extruder screw in this area and extends over a length of approximately 3 to 5 screw diameters. The depth of the groove 24 slowly decreases at its ends until the housing inner wall is finally formed without grooves. In a preferred embodiment, the groove 24 turns in the opposite direction to the screw pitch ( FIG. 2).

By using such a groove in the feed region 9 of the extruder housing 2 , the extrudate to be plasticized and mixed is provided with an enlarged housing wall surface, which improves the feed behavior and thus the pulsation behavior of the extruder due to the increased adhesive effect. In addition, the groove walls can provide an enlarged heat transfer area which, in particular in the case of a cooled extruder housing (see temperature control channel 19 in FIG. 7), largely prevents pre-plastification which is undesirable in the feed area of the extruder.

Reference symbol list:

1 extruder
2 extruder housings
3 inlet opening
4 outlet opening
5 drive unit
6 extruder screw
7 pin cylinder area
8 transfer area
9 Feed area
10 pressure increase range
11 extruder pins
12 screw conveyor
13 housing web
14 processing room
15 worm gear
16 case gear
17 throttle pin
18 screw conveyor
19 temperature control channel
20 housing socket
21 actuator
22 aisle cross-sectional area
23 grooves
24 groove

Claims (13)

1. Extruder for processing and manufacturing rubber and thermoplastic materials, consisting of an extruder housing ( 2 ) with an inlet and an outlet opening ( 3 , 4 ) and a drive ( 5 ) for one in the processing space ( 14 ) of the extruder housing ( 2 ) Extruder screw ( 6 ) rotatably arranged about its longitudinal axis according to main patent 40 39 942, characterized in that the extruder ( 1 ) has two mixing and homogenizing areas ( 7 , 8 ) arranged one behind the other, that one area as a pin cylinder area ( 7 ) pins ( 11 ) projecting radially into the processing space ( 14 ) of the extruder housing ( 2 ) and screw webs ( 12 ) interrupted in the area of the pins ( 11 ),
that the other area is designed as a transfer area ( 8 ), in which the extruder screw ( 6 ) has a continuous reduction in its passage volume from zero to an exit area and then an increase in the passage volume to a maximum value from an inlet area to an outlet area, and in the extruder housing ( 2 ) has uninterrupted housing aisles which increase their aisle volume from zero to a maximum value from the inlet area to the outlet area of the transfer part, in order to then drop again to a aisle volume of zero, and in which the housing aisles are roughly helical around an imaginary longitudinal axis of the extruder,
that in the area of the maximum aisle volume of the housing aisles, radially adjustable throttle pins ( 17 ) are arranged so as to protrude through the extruder housing ( 2 ) and into the housing aisles ( 16 ) and into the processing space ( 14 ),
that in the inlet and outlet area of the transfer area ( 8 ) the number of flights and thus the number of screw webs ( 18 ) and the housing webs ( 13 ) is constant regardless of the housing and the screw flight cross-sectional area ( 22 ), and
that in the feed area ( 9 ) of the extruder ( 1 ) the inside of the housing is provided with a helical groove ( 24 ). 2. Extruder according to claim 1, characterized in that the pin cylinder region ( 7 ) is arranged upstream of the transfer region ( 8 ). 3. Extruder according to claim 1, characterized in that the extruder upstream of the mixing and homogenizing areas ( 7 , 8 ) has a feed area ( 9 ) and downstream a pressure booster area ( 10 ) in which the extrudate can be extru du on the necessary tool impression is. 4. Extruder according to claim 3, characterized in that with a preferred extruder length of 10 screw diameters (D) the feed area ( 9 ) 3 D, the pin cylinder area ( 7 ) 1.5 to 2 D, the transfer area ( 8 ) to 2.5 D and the pressure increase area ( 10 ) is about 3 D long. 5. Extruder according to claims 1 to 4, characterized in that one to five rows of pins ( 11 ) are arranged in the pin cylinder area ( 7 ). 6. Extruder according to claims 1 to 4, characterized in that the transfer region ( 8 ) of the extruder is designed such that the angle between the screw webs ( 12 ) of the extruder screw ( 6 ) and the housing webs ( 13 ) of the extruder housing ( 2nd ) are greater than or equal to 105 ° and do not form angles complementary to 90 °. 7. Extruder according to claims 1 to 6, characterized in that the adjustable throttle pins ( 17 ) are arranged at the downstream end of the extruder ( 1 ). 8. extruder according to claims 1 and 7,
characterized in that the throttle pins ( 17 ) can be moved via mechanically, pneumatically or hydraulically actuated adjusting devices ( 21 ). 9. Extruder according to claims 1 to 8, characterized in that the extruder screw ( 6 ) in the transfer area ( 8 ) has flat and narrow grooves ( 23 ) which connect the inlet-side and the outlet-side screw flights ( 15 ). 10. Extruder according to claims 1 to 9, characterized in that the groove ( 24 ) opposite to the slope in the feed area ( 9 ) of the extruder housing ( 2 ) of the extruder screw ( 6 ) is executed. 11. Extruder according to claims 10, characterized, that the groove width and the groove depth are greater than 0.3 cm, with a groove width of 1 to 3 cm and a groove depth of 0.5 to 1.5 cm is preferred. 12. Extruder according to claims 10 and 11, characterized, that the groove depth slowly counteracts in its end areas Zero decreases, and that the groove is helical over a length of 1 extends to 3 screw diameters. 13. Extruder according to claims 10 to 12, characterized in that the extruder housing ( 2 ) can be tempered by means of temperature control channels ( 19 ).